Continuous method and apparatus for the production of chlorine dioxide



Dec. 29, 1953 E. E. KESTING 2,664,341 CONTINUOUS METHOD AND APPARATUS FOR THE PRODUCTION OF CHLORINE DIOXIDE Filed Jan. 9, 1952 EDE -BEQT E. lzs-rnqe \NV ENTCE.

Patented Dec. 2 9, 1953 smrss ear-Em oser-cs --CONTINUOUS METHOD AND E'APPARATUS FORETHE PRODUCTION OF CHLORINE DIOXIDE lldelbertEi Kesting, Munich, Germany Application January 9, 1952, Serial No; 265,661

Claims priority, application 'Ger'many April 26, 1951 -3 Claims. (Clw 231'52) l 2 -This ifivention' is' directed to a new and imcentration of chlorine dioxide'inthevessel'dravroved method for the continuous preparation of ing the highest temperature, while the chlorine mg l gx and-t novel and improved apdioxide concentration increases in the vessels aims-capable of us in he ry n out f h above thelowermostythe temperature-becoming thod. a lower, and finally the highest chlorine dioxide hlo'rine dioxide is obtained by the reaction *concentration being obtained in-the uppermost "b a ds e a yydrochloricacid, with a 'vessel'wherein thelowest temperature prevails. c o e,"-sodium chlorate being especially em- If'the "lowermost vessel is 'heated' to a giVen =p'loyed. l".na'smu'ch"as chlorine dioxide is eX- temperature the gas-leavingwthis vessel has a tremely explosive at high temperatures, up to w'atervapor tension corresponding to the tem- -J the present timethe' operation has been carried -'perature inquestion. "If this gas-steam mixture out at relatively l'owtemperatures. Despite these *now enters into the next" higher vessel of the low 'temperatures, inorder' to obtain sufiicient "series, it comes into a thermalequilibriumwith iitilization of'thechlorate and'acid, and thus a the contents of that'v'essel, i. =e.,- it-heatsthe wsuilicientyield of chlorine dioxide, there have" vessel and'its contents.- Fromithere the gas curb'een' employed a series of 'overflow vessels, oonrent p'asses into thenext higher-vessel, heating -nected one'behind the other,- in each of which "the lattenand this'is continued throughout the there takes place 'a conversion to form chlorine entire series'of vessels. -In this waythere 'is obdioxide. hlternatively, the operation has been tained in the vessels a -temper'ature gradient -:-.-ca-rried out in -a column. Iii-order to reduce the which automaticallyestablishes itself,-and which danger of explosion, a non-reactive (inert) gas "is dependent on the 'quantity of liquid, air-and is conducted into each vessel, this gas having heat red; It the reaction'liquidis heated in this for its purpose reducing the concentration of --manner-from*vessel to vessel-toa higher temchlorine dioxide in the vessel to a non-explosive perature the result is that the conversion 0f proportion. "chlorate andacid to chlorine'dioxideis very com- In these presently available methods, the utiliplete, and-takes place with the best yield. Dezation of the chemical agents, and thus the. yields spite the highternperatures employedthere is no of chlorine dioxide, have been unsatisfactory. danger of explosion.

'Ihepresent invention solves this difficulty by Furthermore it is possible, in an extremely --means of the surprising discovery that the reconvenient manner, to maintain a-desired given action; between and utilization of the chlorate "temperature gradient in the series of 'vessels it and acid is very satisfactory at elevated tempera- "being merely necessary to control the temperatures, and that chlorine dioxide will not explode, ture at one place, for exampleatthe place where even at high temperatures, if it is sufiiciently th heat is introduced. All othertemperatures diluted with a diluent gas. :15 are then automatically adjusted.

-'-In accordance with my invention, the chlorate The attached drawing: shows, schematically, in and hydrochloric acid solutions are caused to flow Figs. land 2 thereof; apparatusarranged in'casthrough a series of consecutive reaction vessels -cadeintended for the carrying out of-the method. staggered in height, one behind the other, ar- Thesecascades consist,as shown in Fig. 1,'of

ranged either in the form of a cascade, or aslo vessels I; 2, 3, 4,5 andli. "Each vessel is-closed, column. In the opposite direction, a stream of -and overfiow lines 1 lead from the individual inert gas is forced or drawn through the reacvessels to th next following vessel in the series. tion vessels. For example, air or nitrogen may The gas lines l3 are continued with their'gas be supplied as a stream to theseries of reaction 011111811 e s-leading to the bottom of the vessels. vesselsthe purpose of this being to fiush out the -=In"vesse1 I it is intended-that thereprevail, for bhlorine-dioxide produced in the individual vesexample a temperature of' 5"-C.; 'in vessel 2 a eels, and to carry it along, at the same time di- "temperature-of- 40? C.;-in vessel-Satemperature luting it to non-dangerous concentrations. of C. in vessel-4 a temperaturef 30 0 5 The inert gas is caused to flow through the in; vessels 5 and 5 atemperature of 103 C.

Y-liquid 'by means of gas inlet pipes extending to 50 aqueous solution which contains about 400 the bottom of the vessels. The uppermost vessel grams of sodium chlorate and about grams of is'adjusted to the lowest temperature, while the "table-salt (sodium chloride) per liter is introlower-most vessel has the highest temperature. duced in-acontinuous current,.in a quantityof Underthese conditions thecurrent of gas flowliters per'hour and a temperature ofabout --ing-through the apparatushas the lowest con-" 26" -C.,' through linell into the'vessel 'I, from 3 where the solution passes, via the overflow line I, into the next vessel 2. Together with the sodium chlorate solution, there is fed into vessel i hydrochloric acid in a quantity of 58 liters per hour, the temperature being 18 C., through line 20. The hydrochloric acid has a concentration of about 350 grams per liter. The total content of the vessels is such, and the vessels are so dimensioned, that the time the solution mixture remains in the vessels, and thus the time of reaction, is about 1 hour.

In the last two vessels, 5 and 6, steam is blown-in through steam lines 9 and the solution contained therein is heated to the boiling point. The quantity of steam blown in is so regulated that it is suflicient to heat the solution flowing through the apparatus from the initial temperature, for instance 23 C., to the boiling point, and to cover the losses arising by radiation.

Steam discharge lines Ill and H lead from vessels 6 and 5 into vessel 4. Into the steam discharge line it there discharges an air line i2, by means of which air is also fed into vessel 4,

together with the waste steam from vessels 5 and 8. The quantity of air should be so dimensioned that the gas dischargin from vessel i through conduit id contains C102 in the desired concentration, for instance 10 volumetric percent.

Vessels 6 and 5 are heated to the boiling point,

about 103 C., by the steam introduced directly through line 9. Vessel 4 is heated to 80 C. by the steam discharging and entering through lines l and H respectively, taking into consideration the cooling resulting from the admission of air. From vessel 4 a gas line l3 extends to the bottom of vessel 3, and similarly in the case of the other vessels, with the result that the gas mixture moving in counter-current relationship to the liquid heats the content of the preceding vessels 3, 2 and i in such a manner that each preceding vessel of the series, 1. e., 3, 2, i, has a lower temperature than the next vessel of the series.

Owing to the fact that vessels and 6 are heated by direct steam admission, while the following vessels, vessels 4 to l, are only indirectly heated, the desired temperatures are obtained in the vessels.

Other methods can also be used, of course, in order to obtain the desired temperatures in the individual vessels. For example, it is possible to do this by introducing steam directly only into the last vessel 6, or by introducing steam directly into the three last vessels 6, 5, 4, etc.

One may also proceed in such a way that the last vessel 6 is provided with an indirect heating device, 1. e., instead of the introduction of steam, air is introduced in a counter-current direction directly in the last vessel 6. The heating can also be carried out by proceeding so that hot air or some other inert gas is introduced into the last vessel 6.

In any event it is not necessary to provide each individual vessel with a heating device, neither is it necessary to control the temperature in the higher vessels by special means. If the quantity of steam and the quantity of liquid, as well as the quantity of air introduced, are predetermined, the temperature in any particular vessel of the series will necessarily always be a given desired temperature. The temperatures in the apparatus can be regulated in a very simple manner, simply by installing a thermostat 22 at some suitable place, which thermostat controls the admission oi steam in a xnown manner in such a way that the desired temperature is maintained at the place in question, as a result of which also the temperatures at all other points of the apparatus will remain constant. A prerequisite i'or such regulation is, of course, that the quantities of liquid and air which flowthrough per unit of time shall be maintained substantially constant.

As may be observed from Fig. 2, the last vessel I 8 of the cascade has a heating device [4, partially jacketin the vessel. Ihis serves to bring the contents of vessel i8 to the boiling point, which in this case is slightly above C. At the same time the steam which is necessary for the heating of the higher vessels of the cascade series is generated. It is also possible to introduce more heat by means of the heating device than is necessary for the specified purpose, in this way bringin about additional evaporation of the solution flowing through. Air line I2 leads into vessel iii. A steam and air discharge line, I3, leads from vessel I8 to vessel 5. Inasmuch as the generated vapor passing into vessel 5, due to its quantity, would heat the upper vessel excessively, and interfere with the desired concentration effect, a condenser l5 having admission conduit [6 and discharge conduit H for cooling liquid is provided in the airsteam line it, extending from vessel [8 to vessel 5, this condenser serving to condense a part of the steam generated, discharging the condensate as water through a syphon 21. In this way the quantity of steam passing into vessel 5 is metered. This arrangement has the advantage that any quantity of liquid for which the apparatus is adjusted can be continuously drawnofi by the condenser. It is possible, in this way. simultaneously to concentrate the reaction liquid passing-through to a liquid of smaller volume.

Fig. 1 illustrates schematically a series of vessels, arranged in cascade relationship, and the liquid and gas inlet and exit conduits leading to and from these vessels. Fig. 2 represents a modified form of apparatus in which the last vessel of the cascade series, vessel l8 (replacing vessel 6 of the arrangement shown in Fig. 1), is provided with a jacket, partially extending around the vessel, through which jacket a heatin fluid may be supplied for the purpose of heating the vessel and its contents.

Various changes and modifications may be made in my improved method and the apparatus for carrying out that method, certain preferred forms of which have been herein described, without departing from the spirit or scope of the invention. To the extent that they are included within the purview of the appended claims, they are to be regarded as within the scope of my invention.

I claim:

1. The method of continuous production of chlorine dioxide by the reaction of a solution of a chlorate and an acid in an apparatus of the type comprising a series of vessels arranged at relatively descending levels and overflowing each into the vessel next beneath, including the steps of heating from an external source of heat only the lowermost vessel of said series, admitting an inert gas into said lowermost vessel, conducting said gas in counter-current flow direction relative to the direction of flow of said solution, through said solution in the individual vessels of said series, and removing said gas together 5 with the chlorine dioxide produced in said series of vessels, from the' uppermost vessel of said series, whereby the degree of heat will be relatively greater in the vessels having a low concentration of chlorine dioxide, than in the vessels having a higher concentration of chlorine dioxide.

2. The method according to claim 1, wherein the said inert gas passing in counter-current direction is heated before admission to said apparatus and is introduced into at least one of said vessels chosen from those lying in the lower levels of said series.

3. The method according to claim 1, in which steam is introduced into at least one of the lower level vessels and a non-condensing gas is introduced into the vessel next above said lower level vessel in said series.

EDELBERT E. KESTING.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Name Date Mather Feb. 6, 1900 Aylsworth Mar. 2, 1909 Hechenbleikner 1--- Apr. 30, 1918 Walker July 9, 1918 Logan Sept. 27, 1938 Muskat Apr. 9, 1940 Rapson et al Sept. 6, 1949 FOREIGN PATENTS Country Date Great Britain Aug. 20, 1936 

1. THE METHOD OF CONTINUOUS PRODUCTION OF CHLORINE DIOXIDE BY THE REACTION OF A SOLUTION OF A CHLORATE AND AN ACID IN AN APPRATUS OF THE TYPE COMPRISING A SERIES OF VESSELS ARRANGED AT RELATIVELY DESCENDING LEVELS AND OVERFLOWING EACH INTO THE VESSEL NEXT BENEATH, INCLUDING THE STEPS OF HEATING FROM AN INTERNAL SOURCE OF HEAT ONLY THE LOWERMOST VESSEL OF SAID SERIES, ADMITTING AN INERT GAS INTO SAID LOWERMOST VESSEL, CONDUCTING SAID GAS IN COUNTER-CURRENT FLOW DIRECTION RELATIVE TO THE DIRECTION OF FLOW OF SAID SOLUTION, THROUGH SAID SOLUTION IN THE INDIVIDUAL VESSELS OF SAID SERIES, AND REMOVING SAID GAS TOGETHER WITH THE CHLORINE DIOXIDE PRODUCED IN SAID SERIES OF VESSELS, FROM THE UPPERMOST VESSEL OF SAID SERIES, WHEREBY THE DEGREE OF HEAT WILL BE RELATIVELY GREATER IN THE VESSELS HAVING A LOW CONCENTRATION OF CHLORINE DIOXIDE, THAN IN THE VESSELS HAVING A HIGHER CONCENTRATION OF CHLORINE DIOXIDE. 